The present invention relates to a rotor and a motor.
In the prior art, a rotor having a consequent pole type structure is used in a motor (refer to, for example, Japanese Laid-Open Patent Publication No. 9-327139). The rotor includes a rotor core provided with integrally formed salient poles and permanent magnets, which are arranged in the rotor core in the circumferential direction. The permanent magnets function as first magnetic poles. The salient poles are located between the permanent magnets. Further, the salient poles function as second magnetic poles.
A rotor having a consequent pole type structure allows the number of permanent magnets to be reduced and is thus superior since the cost of the motor can be lowered. However, the magnetomotive force of each salient pole is smaller than the magnetomotive force of the permanent magnets. Thus, a difference is produced between the strength of the magnetic field generated by the magnetic poles of the salient poles at the teeth of a stator and the strength of the magnetic field generated by the magnetic poles of the permanent magnets at the teeth of the stator. This lowers the rotation performance of the motor.
Japanese Laid-Open Patent Publication No. 2012-110181 describes an example of a rotor including a first rotor core and a second rotor core, which are stacked upon each other in the axial direction. The first rotor core and the second rotor core each include salient poles arranged at generally equal angular intervals in the circumferential direction. The salient poles each extend in the radial direction (direction orthogonal to axial direction of rotation shaft). In each of the first and second rotor cores, permanent magnets are located between salient poles in the circumferential direction. An annular magnet magnetized in the axial direction is located between the first rotor core and the second rotor core in the axial direction. The annular magnet is held between the first rotor core and the second rotor core. First permanent magnets, which are located between the salient poles of the first rotor core, are arranged so that first magnet poles (e.g., S poles) face the stator. Thus, the salient poles of the first rotor core function as second magnetic poles (e.g., N poles). Further, second permanent magnets, which are located between the salient poles of the second rotor core, are arranged so that second magnet poles (e.g., N poles) face the stator. Thus, the salient poles of the second rotor core function as first magnetic poles (e.g., S poles). The salient poles and the second permanent magnets of the first rotor core have the same polarity as the second permanent magnets and are aligned in the axial direction. The salient poles and the second permanent magnets of the second rotor core have the same polarity as the first permanent magnets and are aligned in the axial direction. Thus, the salient poles of the first rotor core and the salient poles of the second rotor core function as different magnetic poles. As a result, the strength of the N pole magnetic field is balanced with the strength of the S pole magnetic field. This improves the rotation performance.